text:
What is this feature on a Sukhoi Su-27?
Most but not all Russian Su-27's (and variants like the Su-30, -32, -33) have a device that looks like a headlight in front of the cockpit. What is it?

It's the sensor of the IRST (InfraRed Search and Track) system.
An IRST allow an aircraft to search and track aerial or ground targets using passive infra-red radiation only thus reducing the probability of being discovered (for example using a Radar Warning Receiver).
The Su-27 can use it's IRST to track a target at very long distance and engage it using IR homing AAMs like the R-73 "Archer" or the R-27T / R-27ET "Alamo" without using its radar.
Nowadays, many current fighter aircrafts use some sort of IRST, for example the Eurofighter Typhoon.

That is the IRST which can be used for tracking aircraft passively.


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What is a compounding wing and how does it increase helicopter performance?
The US Army is developing a list of enhancements for the next generation Apache attack helicopter. Among them this was mentioned:

Topping the list of major changes is re-engining with the 3,000-shp Improved Turbine Engine, but the array of potential upgrades includes adding a propulsor and compounding wing to increase the helicopter’s performance. Aviation Week

What is a compounding wing and how does it increase a helicopter's performance?

Related: What are the limitations to adding wings with engines to a helicopter?

This paper discusses wing compounding and appears to be a free PDF download.  Apparently the added wing provides lift to offload the rotor, allowing them to work more on providing forward propulsion and relieving some of their need to also create lift.  Figure at the top of page 6 shows the helicopter with added wing with outboard props on the wing.

The compound helicopter configuration, known as the hybrid compound helicopter, features both wing and thrust compounding. The wing offloads the main rotor at high speeds whereas two propellers provide additional axial thrust as well as yaw control. This study investigates the maneuverability of these two helicopter configurations using inverse simulation. The results predict that a hybrid compound helicopter configuration is capable of attaining greater load factors than its conventional counterpart, when flying a Pullup-Pushover maneuver. In terms of the Accel-Decel maneuver, the two helicopter configurations are capable of completing the maneuver in comparable time-scales. However, the addition of thrust compounding to the compound helicopter design reduces the pitch attitude required throughout the acceleration stage of the maneuver.

Image source
The Sikorsky X2 is (was) a compound helicopter, with an engine driven rotor and a pusher type propeller to offload the main rotor.
Image source
The Fairey Rotodyne was a compound autogyro: an engine driven rotor, a pusher propeller, and a fixed wing to generate most of the lift at speed. The fixed wing is efficient at generating lift, reduces the interference drag from rotor lift creation.

source: Stack Exchange

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How strong would a servo motor need to be to power the control surfaces of a fixed wing ultralight aircraft?
I'm looking to build an ultralight aircraft.

The video above shows a good example of how one is controlled with wires or with metal fulcrums/levers, but I am interested if they can be controlled electronically.
My idea of this is that it would work exactly like an R/C plane, but instead of being controlled with a radio, it will be controlled with a joystick through a wired or wireless signal.
I saw the other post that talked about a wireless fly-by-wire system and they said it could be unreliable, but that's not exactly what I'm wondering. I want to know how I can get the supplies to do it and look at the options.
How strong do the servos need to be for such an application? Obviously the rudder, elevators and ailerons will be light, but not as light as an RC plane's, so I can't use servos from a local hobby shop.

Possible duplicate of Would a wireless fly by wire system be practical?

Regarding your follow-up question: wireless transmitters are prone to failure, but in the case of an RC aircraft, nobody dies so the risk is acceptable. I'm not saying you shouldn't attempt this project, but wear a parachute :)

First I'd like to say you are thinking outside the box, not a bad thing...
However for an ultralight aircraft this is impractical. The first problem you have is that most ultralight aircraft don't have electrical systems. Adding one may put you over the weight class for an ultralight. Servo's, batteries, joysticks, etc are also not very "ultralight".
The second thing you need to think about is that R/C's work because a single servo controls two surfaces in the case of ailerons, so they are synchronized. The aerodynamic forces become much, much larger as you scale up, so you will need individual (or multiple) servo's per control surface. Then you need to think about how to synchronize them, and calibrate them.
Next comes in a question of failure modes. If your elevator servo fails, what do you do? What about your electrical system? Dead battery? These FBW systems work on large aircraft because they have multiple redundancies (including traditional cable controls). You won't have the space or weight budget to do that.
It just comes down to trying to shove a complicated system into an uncomplicated aircraft.
And for a little note about "large scale" FBW systems. Usually these systems use hydraulic servo valves, which means that the aircraft includes a hydraulic system (or 3), which are electrically or cable actuated. These can provide sufficient force (along with heavy counterweights) to move the control surfaces. The servo's that you would need would not be available in electrical form since they would need to be powerful, long stroke, and fast. There are servo's that are used in some aircraft for things like flaps, but they are not fast.

That makes sense. Thanks for the comment. The weight and calibration problems seem like they'll be the biggest with this. I still have some questions though... I guess I can't put a paragraph it just posted my comment... So my first question is, how big and heavy does a battery have to be that only controls servos? (answered, thanks) As far as the aileron problem, I could attempt to calibrate the servos so they alternate at the same time, or I could ditch the ailerons and go with a rudder and elevator only style, what problems could that bring up in an ultralight?

Another question I have is what does a large scale RC plane use for "servos" some of these must get up to the weight of some ultralights right? Like this one (http://www.dpccars.com/gallery/var/albums/Large-Scale-RC-Planes/Large%20Scale%20RC%20Planes%20-%2012.jpg?m=1379374575)

Large scale RC's use these types of servo's and they really aren't in the same weight class. The rudder/elevator only would be difficult to control roll, or difficulty with landing in cross-wind. That may be a topic for a new question though (too big for a comment).

"most ultralight aircraft don't have electrical systems" Depends on the definition of ultralight. I'm training in an ultralight, and besides being a two-seater with enough of an engine to cruise comfortably (with me and my instructor) at some 75-ish KIAS, it definitely has electrics; radio, auxilary (electrical) fuel pump, outside lights, FLARM, transponder, pretty much everything you might need in a small GA plane for VFR flight. I suspect you're going by the US definition of ultralight, but don't see anything from the OP that indicates their location, so that assumption might be premature.

I think I saw on YoutTUbe somewhere a few years ago showing a state-of-the-art all electrical servo for fighter jet for a fly-by-wire system. Looked like a big steel box with a massive rod and ball connector coming out of it. Obviously not available for an ultralight.

DC servo's would be best because they can be operated directly from a battery. The higher the DC voltage you can supply the better: 24 VDC is preferable over 12 VDC because of the greater power loading and higher deflection velocity you can obtain.
The servo's would be dimensioned for torque: they need to overcome the hinge moments of the primary flight controls. These are functions of your airspeed, the control surface area, and the position of the hinge relative to the surface chord. For a static elevator deflection for instance:
$$H_e = C_{h_e} \cdot \frac{1}{2} \cdot \rho \cdot {V_h}^2 \cdot S_e \cdot {\bar c}_e$$
With:

$H_e$ = hinge moment (e is index for elevator) [Nm]
$C_{h_e}$ = hinge moment coefficient, function of Angle of Attack, elevator deflection and trim tab deflection.
$\rho$ = air density in kg/m$^3$
${V_h}^2$ = airspeed around the horizontal tail [m/s$^2$]
$S_e$ = elevator surface [m$^2$]
${\bar c}_e$ = mean aerodynamic chord of the elevator in m. Method to construct this is found here - but use elevator/aileron/rudder geometry, not the wing.

$C_{h_e}$ is a bit hard to find, old NACA reports should be useful here. Above is an example of the elevator hinge moment coefficients of a Fokker 27, measured in a wind tunnel. If we fill out the equation with example numbers, we could take 0.2 maximum for $C_{h_e}$; $V_h$ = 30 m/s; $S_e$ = 0.05 m$^2$; ${\bar c}_e$ = 0.05 m:
$$\Rightarrow H_e = \frac {0.2}{2} \cdot 1.225 \cdot 30^2 \cdot 0.05 \cdot 0.05 = 0.28 Nm $$
The surfaces will need to be able to withstand the aerodynamic hinge moment at highest aircraft Angle of Attack, then be able to reach the opposite deflection stop in about 1 second. So the specs of the servo's are:

max. torque = according to above method, substitute dimensions from comparable existing ultralights or the ones from your own design if you have that already.
max. deflection about +/- 30 deg. This is the useful stroke.
max. output velocity 60 deg/sec at full torque. You could use a gearbox for smaller servo dimensions, but the output speed after the gearbox must be > 60º/s.

Please make sure that you have a backup means of aircraft controllability for when the battery fails! Because flight control is vital for survival, the failure considerations are more important than the servo dimensioning:

The servo could fail hard-over, leaving the control surface in one of its stops and ending the flight in a fall. A mechanical spring can bring the surface back close to neutral position when the servo exerts no torque - you would have to dimension the servo accordingly, so that it can also generate the spring torque. Not using a gearbox is better.
Then you may wish to consider what Airbus did with the A320, and leave the rudder actuated by mechanical control, plus make the horizontal tail trimmable.

EDIT
As I understand now, the aircrat will be unmanned during the testing phase. That makes a huge difference: failure mode analysis considers both the chance of a failure, and the consequences. Getting gravely injured because of a flat battery would not be good.
Where to get things is nowadays: the internet. This company makes DC servo's and controllers and sells them on line. Their largest brush type DC servo is about 0.12 Nm, brushless types are smaller and lighter and can be delivered in higher torque values. The torque value from my example is only an example.
It will be possible to use ailerons, use one motor per, and synchronise them. If you would control by rudder and elevator only, you would lean over the wrong way in turns and manoeuvrability would be severely restricted. RC planes have ailerons.

Thank you for the detailed explanation with calculations. That's really helpful, so thanks. .28 Nm is within the spec range of some of the servos that I've been looking at but I think the costs of doing something like this might outweigh the risk. The reason I wanted to do this is to have a safe way to test the ultralight without injuring anyone (thereby using electronic controls and a radio). I might have to make another post asking about that, because it sounds like a pretty crazy idea. Anyway, thanks for your suggestions again, I'm still going to try to make this work, so we'll see.

If in the testing phase the aircraft is unmanned, that would make a huge difference. With failure modes there are always two things to consider: chance of a failure, and consequences of a failure. You don't want a flat battery to be a death penalty.

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What does "inertial" refer to in "inertial reference"?
An ADIRU makes use of air data reference and inertial reference. Inertial reference calculates the heading, position, ground speed and attitude. I was wondering why is it called inertial. Is it related to the term inertia/mass?

yes, based a/a few gyro(s)

It is called inertial, because it works by measuring—and integrating—inertial forces¹, that is forces due to acceleration of the reference frame (i.e. the aircraft). Gyroscopic effect used to measure rotation is also due to inertial forces.
The measured forces include gravity², which can't be easily separated, but this is done by observing that the speed is limited, so the average acceleration must be zero and therefore the long term average equals gravity.

¹ In general relativity the inertial forces are usually considered as real as any other, so the term “fictitious” is not really appropriate.
² In general relativity gravitational force is considered an inertial force. In standard English terminology, gravity also includes centrifugal force due to rotation of Earth.

+1, but "the measured forces include gravity" should refer to the g-force actually not to gravity which is not inertial :-)

@mins, the sum of inertial forces it measures is called g-force. It includes gravity. According to the principle of relativity, gravity is an inertial force. In standard English terminology, “gravity” also somewhat confusingly includes centrifugal force due to Earth rotation, another inertial force. In other words, it is not force due to gravitation, it is the g-force in Earth reference frame. But either way it is inertial.

Might be worth mentioning laser gyroscopes in ADIRUs do not use the gyroscopic effect to detect rotation.

You must be right, I'm not familiar with general relativity and a bit confused with the difference (that I understand now doesn't exist) between inertial and gravitational accelerations. All that seems to be an old story of classical mechanics.

Inertial refers to any forces - Any forces acting on a body which produce an acceleration via Newton's second law of motion ( F = ma ).
In this respect, gravity, is not a force, as it does not produce an acceleration, it only causes a distortion in the geometry of space-time. By Mach's principal, The physics in an enclosed volume in outer space accelerating with one G of acceleration are identical to the physics we experience on the surface of the earth, just as the physics in a free-falling elevator, or an aircraft in a zero-G ballistic trajectory, are identical to the physics in an enclosed volume in free fall in outer space.
From this perspective, which is more accurate that traditional Newtonian perspective, the frame of reference we normally perform calculations in, the earth-bound 1-G frame of reference, is not an inertial frame of reference, as it is always experiencing 1 "G" of acceleration due to the "force" the earth itself exerts on the soles of our shoes.
... The frame of reference of a free-falling elevator, on the other hand, is an inertial frame of reference.
The word inertial does indeed come from Inertia, because the mass of af any body is a key property of all objects in the universe, but it participates in two physical relationships, which ostensibly seem to have no connection to one another. The first one is Newton's Second law, (F = ma ), which says that a body will accelerate when a force is exerted on it, proportional to it's mass. This is the law of inertia.
The second is Newton's law of gravitation, which stated that a body in a gravitational field of another body will experience a force proportional to the product of their masses and inversely proportional to the square of the distance between them.
For many years scientists were perplexed by how incredibly identical the masses measured by these two physical processes were (Force and Gravitation).
It was only when Einstein proposed the General Theory (Gravitation), that this mystery was explained. These masses were the same because there is no force of gravitation. The "force" we think of is a fictitious force, which only exists because we are measuring things in an accelerated, not an inertial, frame of reference (the surface of the earth, which, in space-time, is continuously accelerating upwards at 32 ft/sec2). It is just as fictitious as the force we would think we see if we were in an enclosed spaceship accelerating at 1 "G" In outer space.

https://www.ion.org/publications/online-tutorial-intertial.cfm has my online tutorial for GPS/GNSS and inertial navigation, free to Institute of Navigation members.  This basic material is also available at low cost to nonmembers.
An inertial measuring unit "IMU" typically has a triad of gyros and a triad of accelerometers.  These sensors DIRECTLY provide angular rate and "specific force" (defined shortly), and INDIRECTLY (by propagating the effects fo those direct measurements) provide velocity, position, and attitude.  Gyros sense absolute (i.e., total) angular rate with respect to an inertial coordinate frame (i.e., one that doesn't rotate and doesn't accelerate).  Specific force is the total NONgravitational force; if you dropped an accelerometer it would read close to zero (e.g., a drag effect), not 32 ft/sec/sec down -- and in a cruising aircraft a vertically aligned accelerometer would show the 1-g lift.

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How do helicopters avoid colliding?
When helicopters fly over a city, how do they avoid colliding with each other? For example, after a shooting or accident, both police and news helicopters could head to the same spot.

Something they don't!

If you replace "helicopters" with "cars" you'll have the same problem. Somehow we mostly solved that.

@pipe Wait, we have cars flying over cities yet? :D

@pipe And having an extra dimension makes collision avoidance easier.

@DeepSpace we had them on Oct 21 2015.

Just like other aircraft flying VFR, see and avoid. Helicopters fly slower, which gives them more time to see and be seen.
They also have transponders and ADS-B requirements so it will be possible to see them electronically too (with TCAS today and ADS-B in in the near future).
While helicopters could technically have no transponder and hence no ADS-B requirement, operating inside big cities leads to the under class B veil, which ends up forcing transponder / ADS-B requirements anyway. What I really mean is there's little logic in owning a helicopter that can never go into the big city, those are usually expensive enough to warrant being able to go anywhere, unlike some old cheap piston planes.

IOW, the same way the police and news vans do: looking out the window.

@JörgWMittag: ugh, do vans have transponders now?

Ground vehicles inside airports can have ADS-B transponders.
But general ground vehicles nope, that would be a big waste of ADS-B bandwidth.

It is not far-fetched to think that a majority of ground vehicles will eventually have transponders, considering the rise of autonomous and self-driven automobiles.

A different type of transponder on a separate frequency. In fact most likely some frequency that combines several types of V2V communications.

They are calling that proposed V2V transponder "IoT" and "5G network"

@MarceloPacheco the edit by psmears did not remove any word, it simply adjusted their spelling.

Probably also worth pointing out in a situation like this the pilot will care very little about what's going on on the ground, they won't be staring through a lens or worried about how many people are injured.

@Xavier I thought IoT was only for toaster-to-toaster transponders.


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What is a minimal step angle deflection for flight control surfaces?
If the flight control surfaces (ailerons, elevators, rudder) are controlled digitally by servo motors, yet disregarding the way how the input to the servo motors get generated (manually or autopilot), what is the suggested minimal single step deflection of the control surface to be of practical value for a large UAV or piloted airplane?
By "practical" I mean not a ridiculously small angle that slows down the servo with unnecessary many steps, yet sensitive enough to allow for a smallest practically useful deflection or ensure the precision of a small input.
If the minimal step of deflection is not the same between them, then please suggest your answer for each control. Please give answer in degrees within 360 circle.

Welcome to aviation.SE!

I would suggest find the angle of deflection of the control surface, (such as +/- 15 degrees), and make the servo range match that. So if the servo can move +/- 42.5 degrees from center for example (more than that and you have to worry about reverse movement with  simple control horn), than make it move as smooth as you can over that range to make the control surface feel as analog-like as possible for the piloted airplane at least. When I fly, I don't want any noticeable steps in my control movement, I want the aileron and stabilator following my hand action as smoothly as possible, & rudder.

@CrossRoads that's indeed one of the results I want to accomplish - smooth control adjustments, also efficient and fast controls in terms of electronics and programming. I still hope that somebody has data from experience of the smallest angle deflection - that makes the development so much easier.

servo has no steps, stepper has

one way to implement a good precision servo is to make it and control it as a stepper motor. Stepper is one of the types used for a servo implementation.

Nearly all larger aircraft have servos/actuators that don't have steps in any practical sense, even if they have digital control interface. (That's not to mention aircraft with reversible control, where the pilot moves the control surfaces by muscle force; when they have autopilot servos, the servos are typically controlled by torque rather than position). However, if you build an aircraft with RC-style stepper servos, your question is very valid and deserves special research; I'm just not aware of any. In any case, it will significantly depend on the natural dynamics of the aircraft.

There are several phenomena that may affect the asked resolution. The easier one is the static (steady case), and the dynamic case which requires several more analyses.
Statically, the resolution of any surface will determine the moments that that particular surface can generate. Consider the elevator, the resolution will determine which aoa and which speeds the aircraft will be able to fly (with a given weight and a given thrust configuration).
Dynamically, the stability of the plane will derive the required resolution. Consider the elevator, and suppose your resolution is 1 degrees. The inputs will generate short period and long period (phugoid) modes simultaneously and your controller will become a bang-bang controller, because you can only command increments (decrements) of 1.
Hope these give some clues to understand the physics. For more details, control theory will be useful.

thank you - you well covered the relationships between the controls resolution, surface area, speed and stability. But can you give a simple applied example of the minimal resolution, for example take a composite glider with high l/d ratio - what would be a good practical control surface deflection resolution of ailerons, elevator? Any known numbers from practical experience? Or any example of other 3-axes aircraft with a good L/D ratio (not a supersonic jet)?

I would simply check some rotary servos that are in use with aircraft, e.g. part of autopilot systems or UAV’s. Some of them have ranges in 0.1 to 0.25 degrees. However, the actuated surface resolution depends on the gearing mechanism, as you’d expect.

The correct answer depends on flight speed. If your UAV only flies at one speed: Take the deflection maxima and sprinkle your steps across that range, just as CrossRoads suggested. If you find out during flight test that part of the deflection range is never used, you may consider reducing that range in oder to gain finer resolution over the remaining range.
If, however, the craft covers a wide range of speeds, make sure that you have a finer resolution towards the center of the range. For big deflection angles, it does not matter how close two steps are - you will need them only at low speed and for as long as the condition which you desire to end lasts. At high speed, control effectivity is much larger and even fine variations in deflection angle will result in disproportionally large flight path deviations. Those are unavoidable in a stepped control surface, but should be held as low as practical.
In order to still have a reasonable control reaction, details depend on your servo and the aircraft, so I feel unable to give a concrete number. But make sure that you can react quickly enough in order to dampen out all eigendmodes.

Thank you - these all cover much of the flight specs theory. Good for all who search for this topic here. I personally am familiar with them - I still hope to get a specific practical example. Preferably for a modern glider (for ex. a standard class competition glider) or whatever particular example you know of please share - max deflection and minimal step angles as implemented for different stages of flying (if possible include links to the usual specs of the known aircraft). May be somebody here is from among actual designers and builders who knows actual numbers for a particular design?


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Do aircraft have to be certified specifically for skydiving?
As a skydiver, I have jumped from many different types of aircraft. Most have been specially modified for the sport. Are there requirements outside of the mechanical modifications for an aircraft to be used as a jump plane? Is there some kind of certification for jump planes in the United States?

Not really. You use whatever old beater airplane you can get your hands on with a suitable configuration.  And you may not really need to do a mod like a jump door STC if you're willing to fly with the door removed and the plane is legal to fly that way.
When I was jumping in the late 70s it was from a Cessna 172 that was flown without a door, then later the owner installed a top hinged swing up door available as an STC kit so we wouldn't freeze on the ride up.  Other than that it's just take the seats out.

I think the 208 Caravans operate under an STC to allow 14 pax (sitting on the floor) vs max of 9 in the conventional seating arrangement.

I guess they fly with only a couple hours fuel?

If that... I've watched them:  As soon as the jumpers exit they spiral down aggressively and land well before the parachutes touch down.  Time is fuel, fuel is money!

When I was bush flying it was in a float 180, which can't be loaded to the gills like a 185, and I always flew with just enough gas for the trip, plus 30-45 min. Generally 20-25 gal. Never more than half tanks. That was the only way to haul two pax + their gear.

So is it correct to say that if I can climb out of an aircraft safely, I can jump out of it without breaking any rules for myself or the pilot?

I'm not aware of any regulation in the US or Canada that prohibits it, long as someone is in it to land it, unlike that jackass with the Taylorcraft.  That being said, it's a good idea not to go by anonymous nobodies on ASE if you are legally exposed in some way, and check the regs yourself.

@MichaelHall Parachutists are not considered passengers in determining capacity and do not require seats. They do require seatbelts even if seated on the floor. The installation of these belts can be field approved with a 337 and does not require an STC. The only constraint on the number carried is that weight and balance limits must be respected.


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What would be a simple aerodynamics simulation software for a student?
I have a project due 2 weeks from now that demands we make a glider using Styrofoam. I'd like to simulate the results as I plan my glider before I build it.
Which simple software, which allows importing a 3D model to do the testing on, can give me data on

CG,
CL,
lift,
drag and
reach

based on initial velocity, etc.?

What kind of a project is this? What is your level of knowledge? High school, university? It'll help us answer your question if we know what you know already.

Welcome to SE! The characteristics you ask for are somewhat disparate: $C_L $and such indicate an airfoil analysis program, while range is a higher level performance metric dependent on more factors that just aerodynamics. Also, 3D aerodynamics is a significant step up from 2D, to the point of open source versus proprietary answers. I suggest you narrow down your question, or it may be closed as overly-broad.

I'm voting to close this question as it is about a resource location as stated in the help center: "...it's not about…Where to buy a specific part, "Which headset is the best?", Where can I get a feed of flight-related data? etc."

@ROIMaison, my level of knowledge is quite limited, I've read half of Understanding Flight in a rush for a test but that's about it. It's for my first semester of college. We are building a glider and each team will fly theirs in a closed area.

@AEhere, thank you. I'm sorry for the broadness, I'm a total newbie. Since we're building a real glider I guess it'd be 3D...? I'm a bit lost haha.

If you have only two weeks it may be best not to go running into a maze, but you may wish to have simple and complex approaches running side by side.
As others have said, it would be helpful to know the parameters of your assignment.  Are they interested in the theory, or do they want to see something flying?
The most important thing will be the airfoil shape as far as lift and drag, but glider airfoils are easily obtained on the Net (airfoil tools). Next would be wing loading, which can be obtained from existing models and data from birds.  Design can be your choice, but starting from scratch, a standard sailplane planform will serve well.
Remember to have your CG near your Clift, slightly forward, and your elevator trim slightly up. For an indoor free flight glider a high aspect wing with some dihedral and an upright vertical stabilizer will help make it fly straight.
Although the theory behind gliders is well known, getting one to fly right will be a learning curve from scratch. Leave at least 2 days for test flights, and plan on extra Styrofoam and glue for repairs. Good luck!

Hi Robert! Thank you so much for your answer, it helped a lot. As for the parameters, they want to see it fly. There will be no wind, it has to have a max. wingspan of 40cm, max weight of 30g and the initial velocity will be around 7 m/s. It's a university assignment, I'm in my first year.

Based on the original and a bit too-broad question:
Look into XFLR5, a basic design program that does airfoil design and analysis, and can do some more advanced computations such as stability and eigenvalues. It is mostly useful for glider model design, but can be generalized if you know what you are doing.

Hi AEhere, that's what I was looking for. Thank you! I'm checking it out right now. Sorry for the broad question, I'm in my first year of college and am still learning

A professional software is this: http://darcorp.com/Software/AAA/
From the website:

Advanced Aircraft Analysis (AAA) is a comprehensive airplane design program that gives its users full authority over the entire preliminary design process. From weight and performance sizing to aerodynamics and stability and control analysis, you can monitor all aspects of the design every step of the way.

What you seem to want to do is analyze an airplane before you actually designed it though.

Hey jjack, thanks for the answer. I'll definetly check it out, that's what I was looking for.

@VictorSCS But ask if it'll do styrofoam gliders. A lot of the equations are for big planes.

@jjack will do!!

There are many ways to approach this.  For the bounding I suspect you want, one might try Simulink, which has a model for the DHC-2 and the Cessna 208.  In 2004 I used the model for the Caravan (208) and built some good models very quickly.  Simulink runs with MATLAB.
The Simulink toolkit which the DHC-2 and Cessna 208 models are built upon,  handles flight dynamics and control.
Since 2004, my usage of the above has only been situational and sporadic, but you may find a user group or some such group which can help you kickstart your design effort.

Hey mongo, thank you for the answer. I had seen Simulink before, but didn't know if it was a good idea to try it for a beginner. I got it and am messing around with it, seems to fit the needs. I'll also check out the ones the other answers provided later. Thanks!


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What is the impact of thermal Anti-Ice on descent performance?
I am just another one of the passionate flight simmers trying to understand more about Anti-ice system mechanics. I am talking about the Boeing 737-800 here if it makes a difference.
What bothers me is: Why is turning on TAI systems having negative impact on descent performance? Given a constant speed that we want to keep a shallower descents can be experienced.
Let's imagine a descent with thrust levers in IDLE position. From my research about aircraft systems and jet engines I would assume that turning on TAI would (in that order):
get more bleed air -> less air to burn -> turbine turning slower -> decreased N1
But from what I can experience and read on the web N1 is actually increased instead. I can guess the aircraft it trying to compensate something - but what is it if we're in idle descent? Also, I am assuming the decreased vertical speed comes from somehow increased thrust, which I would also suspect to be lower (or at least kept on the same level as before TAI) not higher than originally.
I understand this is a complex system and each part has impact on each other but maybe you can point me in the right direction ;)

When turning on the Anti-Ice, the demand for bleed air increases and the EEC (Electronic Engine Control) will increase the target N1 to provide enough pressure by injecting more fuel. From the Boeing 737 NG FCOMv2 (7.20.5 Engines, APU - Engine System Description, emphasis mine):

In the normal mode, the EEC uses sensed flight conditions and bleed air demand
  to calculate N1 thrust ratings. The EEC compares commanded N1 to actual N1
  and adjusts fuel flow to achieve the commanded N1.

This impacts the descent performance as explained in the Boeing 737 NG FCTM (4.24 Climb, Cruise, Descent and Holding):

The use of anti-ice and the increased thrust required increases the descent
  distance. Therefore, proper descent planning is necessary to arrive at the initial
  approach fix at the correct altitude, speed, and configuration. The anticipated
  anti-ice use altitude should be entered on the DESCENT FORECAST page to
  assist the FMC in computing a more accurate descent profile.

Note: the above quote is for the 737 NG models. The older 737 classic series does not increase thrust:

Since all engines have been manufactured or modified to use a single idle speed
  in flight, the use of TAI does not increase thrust as it does in other models.

Thanks for the detailed answer. However, I still don't understand where does this increased thrust come from. If N1 is increased in order to restore original amount of air in the combustion chamber to prevent flame out, why is there an increase in thrust? The same amount of air is now burned, and additional air is redirected to TAI. Where does the thrust come from? Does it come from increased bypass air as a consequence on increased N1?

N1 is (more or less) directly proportional to thrust. An increase in N1 will therefore also increase thrust regardless of how much bleed air is used. You will however need more fuel to create the same amount of N1 because some of the airflow into the core engine is used for the bleed and does not enter the combustion chamber. Therefore less air goes through the turbine. Bypass air however is unaffected and this is creating most of the thrust in a high-bypass turbofan.

So to sum it up to make sure I got it right: idle N1 is already at the border value, providing air to the combustion chamber that is absolutely necessary to prevent flame-out. So When we start getting less air to burn because of increased bleed usage, we need to start burning more fuel to get the N1 not only to the original value, but higher to provide the same amount of air into the combustion chamber as before. So because of that amount of thrust produced in the combustion chamber will more or less stay constant, but the increased thrust comes back from the increased bypass air?

@fafaldo Yes, that sounds about right to me ;)

Turning on Engine Anti-Ice causes the engine idle N1 to automatically increase so that it can supply additional bleed air and not flame out.
This means that for descent planning, an earlier descent should be planned since idle N1 is now producing higher thrust.


text:
Why is the maximum endurance for a piston aircraft at sea level?
The Canadian Flight Training Manual stated this when talking about maximum endurance:

For reciprocating engines, maximum endurance is achieved at sea level.

The book does not explain further as to why. Air density is my first guess, when the engine gets a better mixture of air to burn with its fuel, and so we get the most power for the same amount of fuel.
But if that is true then it sort of contradicts why maximum range is at higher altitude.

Endurance is about fly for longer, not faster. At sea level you can also fly slower in order to stay afloat, which decreases the engine power needed already.

At lower power settings the carburetor flap limits air intake.  So at higher altitude one only need to open the flap more (with throttle) and lean to prevent too much fuel from being used.  There is plenty of air at max endurance power settings even if you go up a few thousand feet.

But you have to burn more fuel for the same thrust as you go up, and its a trade off between increased fuel consumption and benefits of increasing IAS TAS spread.  Jets really shine at higher altitudes because their thrust does not drop off with increasing TAS as much as props do.

Try working it from the other end. A propeller needs to generate a certain amount of thrust to maintain a given indicated airspeed to fly.
In thinner air, it must turn faster to do so.
Turning faster is higher RPMs.  Higher RPMs mean more engine friction.
More fuel must be burned per unit time to overcome engine friction at higher RPMs.
RPMs to generate a given amount of thrust are lowest at sea level
(maybe lower in Death Valley (on a colder day)).
Because the horsepower requirement for maximum endurance speed is much lower than the maximum rated output, the horsepower loss due to thinner air is not an issue until one is higher up.  This is why "leaning" is required at higher altitudes.
But "air density" is the correct answer.

What if I told you it's better for max endurance to fly low, even if there were no engine friction?

@Sanchises I'd be interested, although flying in ground effect may be dangerous.  Aerodynamicly, IAS would produce similar drag regardless of altitude.  At max endurance, throttle could be leaned or enriched as needed.  It could make enough power to turn the prop.  There is sufficient air to burn the fuel at say, 5000 feet, because the engine does not need to develop full power.  The prop only needs to spin faster at its IAS to develop the thrust.  But I am willing to hear additional info if there is more.

Fuel flow is largely proportional to engine power, which in turn is largely proportional to power required (there are some efficiencies involved but that depends on the exact combination of engine and prop - we're interested in the general rule here).
Theoretical power required is TAS x drag (not IAS!). Drag is determined by IAS however. So maximum endurance is reached by finding an optimum of the product IAS x drag (VBE), and then making sure TAS is as small as possible for this IAS, which is at sea level.

TASxDrag(or Thrust) is the energy state of the aircraft (per unit time).  Required engine output thrust at a given IAS is constant.  The efficiency (fuel consumption per unit thrust/time) is affected by internal engine friction losses (and prop AOA).  But your statement that TAS should be as small is possible is +.

@Robert I purposefully chose not to include engine and prop efficiency, because those can be significantly reduced (or exacerbated) by designing for a particular flying regime. The things I mentioned are fundamental to flying with a reciprocating engine in Earth's atmosphere.

The following paper gets into the details. Optimum Range and Endurance of a Piston Propeller Aircraft with Cambered Wing
Figure four skips the math and provides a graph.
More than one flight over water has taken advantage of the ground effect when lacking fuel or power, which is an analog of the maximum endurance problem.

The article is behind a paywall, and I cannot see the images either. Can you provide a similar image from the open domain?

Oh, sorry, I thought it was publicly available at no cost.  Give me a day or so and I will get something publicly assessable, or I will excerpt from the document.  Once again, I did not mean for things to be obscured.

Here's one which addresses the endurance calculations, but it lacks a nice graph. The objective is to stay aloft with minimum power, which happens at low density altitudes.  I will keep looking for a better reference.  https://nptel.ac.in/content/storage2/courses/101104007/Module2/Lec8.pdf

Here is a nicer explanation, but still lacks the clear graph.  But it deals with the aerodynamics pretty clearly.  http://www.dept.aoe.vt.edu/~lutze/AOE3104/range&endurance.pdf

OK sorry about all the references, but none of these are perfect.  However in Aerodynamics for Naval Aviators, look at Page 171, and note the bottom figure.  I think the interpretation of that is pretty intuitive for most pilots.  You can see the book here, for free:  https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/00-80t-80.pdf

@mongo definitely recommended reading there. Thanks!

More than one flight over water has taken advantage of ground effect when lacking fuel or power, which is an analog of the max endurance problem. this is not true, if you're lacking fuel or power, you want to maximize range (to get to a place to land), not maximize endurance (time in the air). Unless of course, you want to maximize your time in the air such that you can solve the problem on board, but this is unlikely.

@ROIMaison, I said analog.  When faced with tailwinds, max endurance solutions approach or become max range solutions. But the point I intended to make was that use of ground effect reduced the needed power.


text:
Could airliners fetch data like AoA and speed from an INS?
If I understood what an inertial navigation system (INS) is, it should be able to calculate speed and orientation of the aircraft.
If this is possible, why do airliners solely rely on sensors to measure speed and angle of attack (AoA)?

Since your title references AoA, the body of your question should too-- since this would arguably be more challenging to derive purely from INS, than the other items you mentioned.  (Consider what happens to AoA in a sudden encounter with mountain wave lift for example.)  Note that AoA and "orientation" are not the same.

@quietflyer I agree. I took the liberty to add it to the question in the body.

The “inertial” part of the INS is just another sensor.  The “system” part of the INS blends ALL sensor inputs to come up with the most accurate navigation solution...

An INS gives your speed & orientation in space, but without reference to what the airmass that you're flying in is doing.
The Pitot tube and AOA sensors give speed and pitch orientation in relation to the local airmass, only.
An indicated airspeed of 60 knots, measured by the Pitot tube, may correspond to a stationary aircraft pointed into 60 knots of wind, or an aircraft moving 30 knots over the ground into a 30 knot headwind, or 60 knots of groundspeed in still air, or some other case.  The wings fly (and stall) relative to the air, not the ground, so measurements of air data are vital.

Drift will impede the speed values over time, so INS data can be relied on for short-term uses only.

The question mentions Speed and Orientation which are broad terms that could include:
Group1:
(Air Data sensor + computation)
IAS - Indicated Air Speed
CAS - Calibrated Air Speed
EAS - EquivalentAir Speed.
TAS - True Air Speed
AoA - Angle of Attack
(HDG(M) - Magnetic Heading)^^
Group2a      :
(Inertial/Rate sensor + computation)
GS - Ground Speed
HDG(T) - True Heading^^
TRK - Track
FPV - Flight Path Vector
and
Group2b
(also, Inertial/Rate sensor + computation)
ATT - Attitude (Pitch, Roll, Yaw)
We use the above data for 2 basic purposes:
(i) AIRPLANE FLIGHT & PERFORMANCE dependent on Group1 and Group2b data.
(ii) NAVIGATION dependent on Group2a data.
Some of what you state is possible, and already in use, using Inertial/Rate sensors coupled with computing modules, e.g. INS-like systems or AHRS (Attitude and Heading Reference Systems)
^^ The one prominent example of this, is the Heading (HDG). Inertial/Rate sensor systems have the property called gyrocompassing, ie their behaviour, as governed by the laws of physics, applied to the rotation of the Earth about it's axis,  causes them to automatically align with True North as well as sense the Latitude at their geographic position. Thus the Magnetic HDG displayed on primary flight instruments in the cockpit is actually a synthetic Magnetic HDG provided by applying magnetic Variation from a database locally kept within the Nav Database or the AHRS itself. Such system architecture has done away with Magnetic compass/coil based master/slave systems etc.
Group1 parameters, represent the aerodynamics based flight of the airplane. Why use derived data rather than directly measured, proven and reliable systems, to fly a HDG, ALT and SPD? It is possible to derive a Group1 parameter such as the the AoA, by knowing the Relative Airflow, Pitch ATT from Group2a&b and the wing angle of Incidence. But this is (for want of a better word) a 'contrived' method of obtaining AoA when simple AoA sensor vanes are available and positioned by the the very airflow we seek to know about. The 2 main uses of AoA is to validate the pitot/static Speed data, and provide high AoA alerts. At the present 'state of the art' it is not practical, and it serves little purpose to substitute Air/AoA sensor Data with Inertial derived data except as an alternative in case of an ADC/AHRS system failure. Though we must note that with the advent of 'big data' and 'AI', ie Intelligent systems, this could change. Also, in recent history (last 2 decades), the failure of Group1 type system has proved fatal.
For the record, on some current airliners, when the Baro (Static sensors) measured Altitude is deemed unreliable, a GPS derived Altitude is available for display.

If I understood what an inertial navigation system (INS) is, it should
be able to calculate speed and orientation of the aircraft.

In reading some articles about the 737 MAX I found out it is possible to derive AoA from other sensors but it will take more than the INS to get enough data to calculate this.  AoA sensors tell the crew how the aircraft is moving through the air.  Knowing where you are, the speed and direction relative to ground, and the position of the various control surfaces, is not enough to know AoA.  It's going to take some measurements of the air movement as well.  I don't know precisely what is the minimum required for this but an educated guess would be air pressure and air speed.
INS will tell you position and movement in relation to the ground, not in relation to the moving air.

If this is possible, why do airliners solely rely on sensors to
measure speed and angle of attack (AoA)?

Part of the problem is that getting a new computer certified by the FAA is really hard.  It's simply easier to get redundant sensors certified than the computers needed to calculate this information.  This makes sense on some level because if we are to assume that hardware fails then how are we to know a calculated value is any better than a measured value?
As I recall Boeing has used AoA sensors on both sides of the aircraft, up near the flight deck, for some time now to provide redundancy.  AirBus has used three for a long time, two near the front like Boeing and the third closer to the tail.
With Boeing there's an AoA disagree warning if the two sensors are outside of an allowed error margin between the two.  While it is certainly helpful to know when the AoA reading can no longer be trusted it is more helpful to know what the AoA measurement should be.  This is why AirBus has three sensors, a single sensor failure will not leave the crew without this information.  With two sensors and a disagree warning the crew cannot know which reading to trust.  With three sensors and a disagree warning then the two that agree can be trusted.  If all three disagree then it's the same problem with two and one not working.  This is not good but as I understand it not something to declare an emergency over, AoA measurement is not considered critical to safe flight.
The FAA, Boeing, and apparently a well trained crew, consider AoA information "nice to know" as opposed to critical to flight.  This is why the FAA only requires two AoA sensors and an alarm that the reading is not reliable.  Airbus, and some airlines, consider an AoA reading important enough that there are three AoA sensors on AirBus aircraft and this information is available to the crew.  Boeing has AoA information available to the flight computer but it is not available to the crew unless the airline asks for that information to be displayed.
Because of the 737 MAX crashes it sounds like all future passenger aircraft will be required to have AoA available to the crew, and triple redundant sensors.  AirBus already has three AoA sensors so they likely have little or nothing to do to comply with this requirement.  It will be interesting to see how Boeing complies.  I suspect all 737 MAX aircraft will have three AoA sensors before allowed to return to flight.  Other Boeing aircraft could have another AoA sensor added or they can have a "virtual" AoA sensor by using information from other sensors and calculating the AoA value.  At least one Boeing engineer thought it possible and beneficial to have a virtual AoA sensor when the investigation into the 737 MAX MCAS problem was going on.
What it comes down to is that the FAA, airlines, and flight crew all know that hardware can fail.  Even if we assume software is flawless it depends on working hardware to function as it should.  Whatever sensors that could be used to calculate AoA could fail so there would have to be some redundancy somewhere to detect this failure and still provide critical information to the crew.  If we were to consider AoA critical to flight then having at least one AoA sensor would be wise to verify the calculated value.  Having two AoA sensors means one AoA sensor can be lost and still have a verified calculated value.  Having three AoA sensors means not needing to calculate the AoA value, it means having a way to verify each against the others.
Aircraft have had two of every flight critical sensor for a very long time.  This left the crew with confidence in their measurements so long as everything agreed.  Because some of this information overlaps it's generally possible to find which sensor is wrong if there is a single sensor failure, or no two sensors of the same kind fail.  With a capable enough computer the process of eliminating a failed sensor can be automated, but the computer can fail too.  This means two flight computers and three of some sensors.


text:
What are the procedure for a B747-400 wheel change?
And what are the required tools? I am fascinated by how you do a B747-400 wheel change.

https://youtu.be/Bh6-1qL6dgY

Jack up a wheel. 2) Unbolt old one. 3) Bolt on new one. 4) Lower jack. Source: Watched it being done while standing about 50' away on the tarmac of Ben Gurion Airport c.1984, while waiting to load our dogs to fly home to the USA. (Security, even in Israel, was different then.)


text:
Would a lighter aircraft require the same amount of power than a heavier one to fly at the same speed?
I had a question come up:

If aircraft A is identical to aircraft B, except that aircraft B weighs 200 kg more. Which of the following statements are true?

The answer I selected was wrong:

Aircraft A would need less power to fly at the same speed as aircraft B

I pictured that with less weight, a reduced angle of attack would result in less drag and hence less power? Would anyone be able to “lighten” me with this?
Thanks for the feedback, it may have just been a typo..
The 4 multiple choices where:
1) Aircraft A would need less power to fly at the same speed as aircraft B
2) Aircraft A would need the same power to fly at the same speed as aircraft B
3) Aircraft B would have poorer climb performance
4) Aircraft B would require a longer runway for landing

Your response is true as long as both aircraft fly at or above minimum drag speed at the speed in question.

It looks like your choice was correct, and there is an exam typo, but usually multiple guess (er.. choice) questions include at least 4 choices.  If you can, edit your post to list all of the choices.  They are always structured so that there is a right one and an almost right one, while the rest are obviously wrong.  They are designed to force you to think through the question carefully to choose the correct one over the nearly correct one, and if you can't because you don't know the material well enough, chances are you will pick the wrong one.

I believe this is likely an error in the test. At any speed, whether above or below Minimum Drag speed, the heavier the gross weight at that same speed, the higher the AOA, and therefore the induced drag. Form drag, as the aircraft are identical in shape, would be identical, except for a very slight difference because the frontal presentation might be very slightly different due to the higher AOA.  What was the "right" answer? What were the other choices?

I'm unsure of what all is included in "identical," but it would have to include the c.g. to properly compare the two. If they're completely identical, including c.g., the heavier aircraft will need more power, burn more fuel. However, if the lighter aircraft has its c.g. up against the forward limit and the the heavier aircraft has the c.g. up against the aft limit, the lighter aircraft might burn more fuel if the aircraft is of what we usually think of as the common type, i.e. the tail is providing a downward force to balance the lift of the wing.

The question asks, "Which of the following statements are true?" Note: statements are, not statement is. Is it possible there was another true statement in the list and you were marked incorrect because you did not select both of the true statements?

@CptReynolds: No, even below minimum drag speed the lighter aircraft needs less power.

@PeterKämpf I think you are correct and I must have been not quite awake when posting.

You are right. The heavier aircraft needs more power. With one exception.
The power needed to keep an aircraft in the air is the product of flight speed and drag. When flying at the same speed, the drag of both aircraft is crucial to answer the question. Since both share the same geometry, it is safe to assume that both have about the same friction and parasitic drag. But the heavier aircraft needs to fly at a higher lift coefficient in order to carry its higher mass, so it will create more induced drag.
The one exception is when both aircraft have a highly laminar airfoil with a pronounced drag bucket. If the flight speed is picked such that the heavier aircraft will still fly within this drag bucket but the lighter aircraft will fly at a lift coefficient below the lower boundary of that drag bucket, the difference in friction drag could be higher than the difference in induced drag (which is small at high speed). But that exception would need to be made clear in the question.
To fully judge the correctness of the test, please provide all answers. As @David K suggests, your error might have been not to select all correct answers.

Thanks for that! Yes here are the options, and multiple answers can be selected.. I selected A,C and D.. so it may have just been a typo!
a) Aircraft A would need less power to fly at the same speed as aircraft B
b) Aircraft A would need the same power to fly at the same speed as aircraft B
c) Aircraft B would have poorer climb performance
d) Aircraft B would require a longer runway for landing

@Jesse: I agree with your selection of answers.

At constant speed the forces of thrust and drag are equal. Since F=m*a, the ratio between accelerations due to these forces is the same regardless of mass. Therefore, they equalize at the same velocity (drag is dependent on velocity) - no more thrust is needed to counteract decceleration due to drag

Maybe my nearly-80 year old brain isn't functioning properly, but I don't see how this answers the question. And, if you're saying, in effect, that a 747 in cruise at mach 0.86 at 700,000 lbs doesn't burn more fuel (more power) than one at 600,000 lbs at the same speed, I can assure you that is incorrect.


text:
Is there a rule of thumb for reading AGL vs MSL?
Recently, I read that as it pertains to directions: if you read it, it's true, if you hear it, it's magnetic. This is mostly correct, one edge case though is runways are written/drawn with magnetic direction.
Is there a similar rule of thumb for altitudes in MSL vs AGL?

I can’t say I understand what you are talking about.  AGL ie equal to MSL reading minus local field elevation directly below the aircraft.  Radar altimeters display altitudes in AGL.

I think the answer to the question is simply, "no".

@CarloFelicione I just mean that in aviation, there are some things reported in AGL and some in MSL, in the same way that some directions are reported in "true" and some "magnetic". I was curious if there was a similar rule of thumb but it seems that there isnt

You can’t generalize about magnetic/true. The written/spoken only applies to wind direction in weather reports. The one exception is wind direction reported in PIREPs where it is reported as magnetic whether is is written or spoken. It does not apply to charts and ATC. Airways are based on VORs which use magnetic direction.  Approach and departure charts all use magnetic direction. Even RNAV charts show magnetic direction. And ATC will always give you headings based on magnetic headings.

I don’t know that you can generalize, but there is a general tendency to report things as MSL unless you are close enough to the ground that you might hit them.
For example, on VFR charts in the US, manmade obstacles show both MSL with AGL in parentheses below it. If you are flying along and there is a radio tower, it makes sense that you might want to know how high above the surrounding terrain it is.The highest point in the terrain on the other hand only shows MSL.
NOTAMs for obstacles around an airport show the AGL first and then MSL. When you are doing your pre-flight planning, knowing how high you need to climb above the field is probably of more use to you than knowing the MSL value. e.g. if an obstacle two miles from the field is 300’ AGL you know that you need to climb more than 150’ per nm in order to avoid it.
Traffic pattern altitudes are usually 800 or 1,000’ AGL but expressed as MSL. It’s good to know for planning purposes how high above the ground you will be, but (in the US at least) you use MSL on your altimeter to fly the pattern.
IFR charts all depict altitudes in MSL. Approach charts (US TPPs) do show AGL below the MSL values. You can always calculate the AGL value from the MSL and field elevation, but having it on the chart gives you a heads-up as to how high above the field you will be if you fly an approach to minimums.
Weather follows the same general principle of “the closer you are to the ground, the more likely you are to be interested in AGL”. If you listen to the ATIS, you are given ceilings and cloud cover in AGL. However, when planning your flight, winds aloft are given as MSL. That makes a lot of sense since the forecast is for a wide area where the terrain can vary tremendously.

Simply this: there is no such thing as "altitude AGL". Altitude is always AMSL, height is always AGL, and flight levels are always with reference to setting 1013 on your altimeter subscale.
Whenever anyone gives you a level, they should explicitly call it an "altitude", "height", or "flight level". The exception is if they say something like "3000 ft on QNH 1004", which is always an altitude; in the UK, the inverse is true for "1000 ft on QFE 1002".

QFE heights aren't height AGL, it's height above an aerodrome reference location. This is important when there's terrain. Ideally this is height above runway, but that may not be true.

That's true, but you would usually only be on QFE in the vicinity of the aerodrome anyway. Since it's only a local term I don't feel the need to explain it too much.


text:
Why do airliners have to park so accurately?
I was watching some airport documentary and I noticed that the planes always had to park precisely. I honestly didn't think so much of it before, but in the documentary, an aircraft parked badly because the VDGS couldn't detect it correctly due to fog, so it had to be pushed back to park again with the help of a marshaller.
The only two reasons for this I could come up with are the following:

Jetways: I figured it's because of the jetways, but they can move about so as to adapt to where the plane is. Plus, when parking on stands, the accuracy is the same and there is no jetway.
Aesthetics:  I also thought it could be about aesthetics, but the systems used to help the pilot park (a marshaller or VDGS) can be expensive so business-wise, it wouldn't make sense to be so strict on parking if it's just for the looks.

This is to ensure that there is space for all equipment around the aircraft. It's not critical to the centimeter, but if it's off by a meter or more there may be problems. For example, the tail may stick out into the taxiway behind or the nose may stick into the service road in front of the aircraft. While most aircraft stop with the nose wheel on or very near the stop-mark, the main wheels can be off by a few feet, depending on how early/late the pilot turns into the stand.
Modern aerobridges have a wide range of movement to cater to various aircraft types, but nowadays there is a lot of equipment buried in the ground. You might see ground power and air conditioning hoses which plug into the ground next to the aircraft nosewheel area. If the aircraft is off by a few feet the hose/wires may cause obstruction to the ground crew. The hydrants for fuel also need to be near the fuelling ports - too far and the hoses might not reach.

“Its not critical to the mm/foot” is kind of a weird statement—1 ft is over 300 mm. American measures don’t really have anything comparable to millimeters, fractions of an inch are used but those aren’t units. And even an inch would be over 25 mm. Since millimeters were used in the question, it might just be easier in this case to stick with metric.

@KRyan: Some industries use "mil" quite a bit (1mil is 0.1", i.e. 0.0254mm), and can use the phrases "dozen mils" or "hundred mils" as units of length measuring about 0.3mm and 2.54mm, respectively; such phrases accommodate constructs like "a few dozen mils"  Metric, so far as I can tell, lacks anything between "millimeter" and "micron".

1 mil is actually 0.001" (1 thousandth of an inch)

The apparent accuracy the OP was talking about may be due to a known psychological effect.  You can aim a gun more accurately if you aim for a point rather than a box.  Likewise, it may be easier to get planes in their place every time, if they aim for an absurdly small target, rather than aiming for the actual box of acceptable positions.

@supercat There is no such unit as "micron" (outside of Battlestar Galactica, ofc). "Micron" is how some people mispronounce "micrometer", probably hoping it would make them sound as cool as Adama.

@Agent_L Micron is the proper term in much of biology. See also https://en.wikipedia.org/wiki/Micrometre#Continuing_informal_usage_of_micron

@forest What part of the article are you referring to, because I can't find anything except "officially revoked"? Also, I think "widespread" would be a better term than "proper". "micron" is improper in any use, but surely it's still used widely. Perhaps my BG joke wasn't as funny as I intended : )

It's "proper" enough that it's found in textbooks, research papers, micrograph illustrations, etc., even if it may not be the official term for a millionth of a meter.

@Agent_L: By the same logic, one should refer to "square hectometers" rather than "hectares".  Pronouncing four syllables for "micrometer" rather than two for "micron", when the latter is perfectly understandable, is needless verbosity.

US please please change to metric system!!

"millimetre" was removed from the question yesterday. I would suggest sticking with a single measurement system.

@Agent_L, Some people and some dictionaries. The dictionary that I bought in 1972 (six years before Battlestar Galactica, for whatever that's worth) defines "micron" as "The thousandth part of one millimeter."  The Google Ngram chart for "micron" shows it gaining in popularity throughout the industrial age, until right around when the Système International was created, and then slowly tapering off since then.

@supercat No..... mil is 0.001", the same as "thou" (you got the mm right). 0.1" might be a "tenth" though to a precision machinist a tenth is "0.0001"). Ain't it great?

@SpehroPefhany: Silly typing mistake.  I used to work (and still prefer) working with parts that use 100-mil (0.1") spacing.

I worked for 3 years as a ramp agent and there are two reasons:
Jet bridges and safety.
Jet bridges have plenty of leeway, but not a lot.  This gets worse in winter because those things hardly move at all with ice.  Some jet bridges are poorly engineered, some are old.  The painting on the ground tells the marshaller where to park the aircraft.  By putting the forward landing gear on the right spot, you ensure that the jet bridge will reach the door and line up.  Furthermore, it increases efficiency because the operator won't have to do as much adjusting to get the bridge into place, allowing for a smoother transfer of crew and passengers.
The bigger reason is safety.  The painting on the ground determines where suction and jetblast are dangerous.  By keeping the plane aligned with the markings, you keep your fellow ramp agents safe while they wait for the aircraft to park and turn the engines off.
Of course it isn't so bad as "a milimeter" off.  You can miss the marker by 1 or 2 feet and still be fine in most cases (of course, your fellow ramp agents will make fun of you the rest of the day, but that's besides the point.)  But the primary reasons are jet bridge limitations and safety.

Welcome to Av.se - nice answer.

The suction and jet blast areas don't make sense because the distance between the engines and the main door varies widely depending on model, consider a 737-600 and a A340-600. It may be something implemented for airlines that have few types, but it can't be done on a general basis.

I would agree except most airports have stands of different sizes, which means that all aircraft that "fit" in one specific size will usually park at stands of that size, allowing those markings to be accurate most of the time.

@user71659, in general that's true, however, each gate is usually marked for a select few aircraft that the gate is expected to regularly service, thus the markings are generalized for those aircraft types.  For example, the JetBlue gate at PWM is only set up for the A320 and the E190, because those are the only two aircraft JetBlue operate (as of when I worked there anyways.)
But yes, if a different type of aircraft that wasn't anticipated tried to park there, then the markings on the ground wouldn't be valid.  At that point, you have to rely on your judgement.

Bounty for real-world, real-facts answer, thanks

To add to Anilv's answer, here's a prime example of what happens when a jet isn't positioned correctly on a jetway (it's not parked, but the same principle applies)

Or this Royal Jordanian clipping a parked jet

The 'fender bender' happened when the Royal Jordanian Boeing aircraft's nose and wing hit the tail of the ChautauquaAirlines flight which was parked at a gate.

And a fender bender could easily cost an airline hundreds of thousands in lost revenue alone (downtime for repairs) even if the damage is small

It's a plane vs ground equipment issue too

@user71659 RIP.

Regarding user71659's comment, if that is indeed an A332 as marked, a 'total loss' would be waaaaayyyy more than the $30M that posts mentions. More like 10x that figure.

In addition to all of the reasons already mentioned (jet bridge alignment, alignment with safety markings on the ground, positioning relative to ground equipment, and staying out of taxi lanes,) another important reason for jets to be parked accurately (laterally) is keeping their wings in the proper bounds.
Jet airliners tend to have rather long wings. When you're parking a bunch of said jet airliners in a row, you need to make sure that each of their wings will stay within the proper bounds so that they don't clip either ground equipment or the wingtip of one of the adjacently-parked aircraft. Each parking stand is designed for aircraft up to a certain wingspan, so, as long as the aircraft are parked correctly, an aircraft within the size limits for its stand is guaranteed not to clip wings with the adjacent aircraft if it is parked correctly. If it is not parked correctly, all bets are off.

We certainly had that issue at PWM where I worked.  I worked for United (gross) and United controlled Gate 2.  We frequently parked their Embraer 170/175s there.  Next to us at Gate 3 was Southwest, who only operates Boeing 737s.  We'd often need to coordinate with the Southwest rampers and the fuel truckers to get equipment maneuvered and out of the way when we both had aircraft on the ground at the same time.  Wingtips came very close, like maybe ten feet between aircraft, if that.  It made push back operations rather intimidating.  Another good reason why its important to park a plane well.

In addition to all the answers stated here, even in airfields where there are no fixed ground equipment, the reason the aircrafts must park accurately is to get the best use of the available space. If the airfield is crowded, each extra parking spot or free taxiway is a bonus. If everyone park their aircraft like some people park their cars however they want, the amount of aircrafts an airfield can receive will decrease.


text:
How can I calculate the lift force on an aircraft pulling out of a dive?
Any ideas on how this question is answered?

Consider an aircraft dived [sic] along a path inclined to horizontal,
  perhaps even a vertical path. The manoeuvre whereby the aircraft
  recovers from this condition and is restored to level flight is known
  as a pull-out. Calculate the maximum and minimum theoretical lift
  force and its geometrical position in terms of the load factor n.

Um... how simplify is the model they are asking for? The easiest way is to assume the trajectory is circunference, its radius depends on the load factor. The really right way to do it is to consider that the airplane will use the maximum lift of the horizontal control surface.... if this is the direction I can develop further

This sounds good to me. Thanks.


text:
How does ice affect the combustion systems of jet and piston aircraft engines?
What are the effects of ice on a jet and piston aircraft engine? I've tried Google but I'm not satisfied with the results.

Ice effects the carburetor of a piston engine, is that what you are asking about?

Welcome to aviation.SE! I'm not sure what you're asking, but this question may answer the jet part, and this one the piston part. You might like to take the [tour] to learn more about how the site works. As it is, your question seems quite broad; if you can make it more precise and also tell us why Google didn't help you so far, that would help us to give you better answers.

For piston engines, icing can obstruct the carburetor throat, reducing air to the engine.  Fuel injected engines are less prone to ice but it can accumulate on air intakes and engine air filters.  Carbureated engines have carburetor heat, which heats the induction air prior to entering the carburetor.  This eliminates or reduces icing at the expense of richening the mixture due to the decrease in air density due to heating.  Fuel injected engines usually offer an alternate air source for the engine which is less prone to icing than the primary but reduces the available manifold pressure for a given throttle setting in the process.  Alternate air intakes are sometimes also available to turbocharged engines to prevent compressor icing as well but may reduce the critical altitude of the turbo in the process.
Turbine engines can collect ice on the fan and/or compressor stators and rotors - al least the first or second stages of the LPC, increasing the risk of a compressor stall.  Icing can also accumulate on the engine inlet, reducing airflow to the engine.  Anti icing measures can include heating engine intakes using compressor bleed air to prevent ice accumulation


text:
Why are jet fuel prices very similar in North America and Europe, yet automotive fuel prices are very different?
Why is the pricing difference of jet fuel between North America and Europe extremely small, unlike automotive gasoline?
As of June 22, 2018, the prices in USD per barrel of it between the two continents are 88.0 and 87.8 and slightly older data confirm the existence of a small difference (I have not encountered a comprehensive dataset). Yet automotive gasoline in Europe usually costs 2-3 times the price it does in the US, comparing each US region to the very roughly analogous European one (based on income, geography, etc.). Why is this?

Welcome to Aviation SE!  While this question impacts aviators this question falls more in line with economics and they Economics Stack Exchange may be the more appropriate forum to ask this question.  See https://economics.stackexchange.com/

@DLH Sorry---yes, that is what I was looking for---I was unfamiliar with the other subfora, and decided to simply post it on this familiar one.

Europe claims to deliberately raise the cost of automotive fuel to help discourage automobile use (studies show it does not work). The total US tax is ~$0.50gal while Europe averages ~$3.00gal. https://taxfoundation.org/how-high-are-other-nations-gas-taxes/

Jet fuel for international commercial aviation is effectively not taxed due to an agreement between ICAO member states. (See here ICAO PDF  ). Therefore the prices closely track to cost of production and distribution. These are similar worldwide. Differences exists due to local taxes on companies, difference in costs of transport, effects of competition on price etc, but these effects are limited.
Automotive fuel is taxed. I am originally from the Netherlands, where we have one of the highest taxes in the world when it comes to fuel taxes. Petrol costs at the moment approximately 1.66 Euro/litre, of which 68.84% is taxes.
In the US, the average total tax (federal plus local) is \$0.4818 on a gallon of gas (equivalent to \$0.1289 per litre).
So the difference in tax makes most of the difference in automotive fuel prices.
Sources: wikipedia

Is there a way to rationalize this inequality?  Are European consumers of jet fuels imposed a separate carbon and pollution externality tax?

@RuslanNabioullin, the tax is not so much pollution tax as infrastructure tax. Roads are paid from public funds, and the need for investment in roads is closely correlated to the miles driven, so it makes a lot of sense. Airports and ATC services are however paid separately, so there is no point in such tax for aircraft.

Re "In the US, the tax is 48.18", that might be the federal tax.  In reality, states and localities within states add their own taxes on top of this.  (For instance, there's about a 30 cent/gal difference between same-company stations 15 miles north & south of me, due to different city & county taxes.)  Also in some states, there's a tax on aviation fuel too, that goes to support airports &c.

Automotive fuel prices are also very similar between the US and Europe, when comparing pre-tax figures. For instance:

The current pump price for regular gas in Pennsylvania is \$3.00/gal, of which \$0.77/gal is tax (\$0.184 federal + \$0.582 state), making a pre-tax price of \$2.23/gal.
The current pump price in Germany is €1.47/L. Before 19% VAT that's €1.23/L, and less €0.65/L fuel tax, the pre-tax price is €0.58/L, which at the current rate of exchange is $2.55/gal, about 14% higher.

The difference is simply that the total effective tax rate on gasoline in PA is about 35%, while in Germany gasoline/petrol is taxed at an effective rate of 153%.
For jet fuel sold to airlines, on the other hand, both places offer much more favorable tax rules, so as not to cripple the aviation industry. The total tax applicable in PA is $0.03/gal, and my understanding is that in Germany, both fuel tax and VAT are entirely refundable for airlines, so the net tax is zero. Since the taxation is minimal in both cases, the drastic difference in taxation doesn't exist, and so the drastic difference in retail prices also goes away.
Aviation gasoline tends to be treated more like other gasoline, and private pilots generally don't qualify for tax exemptions (and the price of avgas is rather high to begin with), so the differences there may be much more drastic from place to place than with jet fuel.

It's not to cripple the aviation industry - politicians would be happy to tax jet fuel if they could. But then the airlines would fuel up in cheaper places. Arbitrage would make any local tax increase impossible. Note that aviation gasoline is also heavily taxed in Europe, because the limited range of GA aircraft makes arbitrage much harder.

Airlines are very careful not to load more fuel onto an airplane than it needs to make the hop, plus reserves, because overdoing the fuel load amounts to burning extra fuel to carry unnecessary fuel.  What would happen if the various European states and municipalities started taxing Jet-A is that airfares to and from those places would rise, fast, to cover the taxes and headaches.  This would in turn cause tourism and business traffic to those places to drop, which would cause MAJOR political heartburn.

@Peter Kämpf: Not necessarily so.  See my above comment about the about 30 cent/gal auto gasoline difference between two localities about equidistant from me - yet the gas stations in the more expensive one haven't gone out of business.  And in the same localities, 100LL is $5.89 in one, $4.99 at the other (and $4.89 at another nearby airport), which means a $40+ difference filling the Cherokee.


text:
For general aviation small aircraft flying VFR under 10,000 feet, can I use my phone GPS for navigation in the US?
For general aviation small aircraft flying VFR under 10,000 feet, can I use my phone GPS for navigation in the US?  So no onboard GPS (which are expensive), no VOR/DME, of course there is always dead reckoning and pilotage.

My first thought is "Dunning-Kruger Effect", people overestimating their own skills...

I've navigated half way across the US a few times with my phone being the most advanced piece of navigation equipment in the cockpit. Yes. It can be done but I would limit it to VFR only.  As with most things in aviation: just don't be dumb about it.

Can you do it? Sure. It is recommendable? That depends.
If you are planning to use it as your primary source of navigation, then I would say definitely no. Aviation GPS units are designed to be used on aircraft, they are reliable and have airspace maps. There's a reason they are expensive. The same cannot be said for your phone GPS.
But, if you remain aware of your position by other means (visually recognising landmarks and cross referencing them with aeronautical charts) then sure, you can use your phone GPS as an additional source of navigational information.
Just keep in mind that if the GPS suddenly fails, you should be able to continue the flight normally. If you can't, then it means you are trusting the GPS more than you should.

Thanks.  Just to elaborate.  Are there some software on the phone/tablet that contain airspace maps (locally) and can't I just use that to navigate?

The sudden failure applies to aviation GPS as well, which is why it's a good idea to make pilotage your primary means of navigation.  (You might also consider the cautionary tales of people who've followed their automotive GPS systems into canals, down cliffs, into deserts or deep snow...)

@ShuhengZheng - Ditto what James said. Apps like Foreflight, FlyIQ, FlyGo, Stratus Insight, etc. are EFBs that can contain any and all charts that you need for the entire world (as long as you have the storage space). Foreflight on my iPad takes up between 25-50 Gigs of space. It contains charts for the entire US and then some. All of your flight planning can be done on it. And, except for updating your charts, getting your weather briefing, and filing your flight plan, it does not need a data connection to operate. It & a Stratus make a great tool and backup. Still, rely on your pilot skills.

@Dean F.: OTOH, paper maps never experience battery problems :-)

"You might also consider the cautionary tales of people who've followed their automotive GPS systems into canals, down cliffs, into deserts or deep snow"- were they not looking out the window?!

@user253751 they were trusting the system. What else would they do?

@user253751: I'm sure I don't know what they were doing, or thinking - if indeed they were thinking at all.  I just see news accounts of their rescue or body recovery :-)

A handheld (or yoke-mounted) GPS such as the Garmin 76S (very ancient now) is very inexpensive and quite useful for VFR navigation, especially for choosing the right heading to end up where you want to go despite crosswinds, and for estimating ETA. For seeing airspace boundaries or having quick access to the location of nearby airports in case of an in-flight problem, something fancier like the IFly700 (also ancient now) is more practical and still not expensive.  These days programs similar to what is available on the IFly700 can be run on inexpensive tablets.  Using something like one of these options as an inexpensive independent tool in addition to your phone would give you a substantial amount of redundancy and help support a "yes" answer to your question.
You may find it most practical to rely mainly on your phone while keeping the other device stashed away somewhere where you can reach it easily if the phone stops working for some reason, or you may find it advantageous to keep the other device powered up and running in addition to your phone.  I've even used two devices at the same time while flying a hang glider, which seems like complete overkill, but there were definite advantages to being able to see two screens displaying different sets of information at the same time without pushing any buttons to switch back and forth.
You may find this ASE question to be related/ helpful-- Why might a moving map Android app consistently record altitude off by 120 feet? .
You may have better luck finding information about good apps to run on your phone for in-flight navigation as well as for saving a record of your flight-- and there are many-- in various sport pilot discussion forums, perhaps the EAA forum, etc.  Answers to your present question will likely focus on "is it a good idea to navigate this way?".

The answer is yes you can use your phone for navigation, if you remain VFR in VMC in the US National Airspace Space. You just must continue to maintain visual reference to the ground and be able to abide by airspace rules (don’t bust any controlled airspaces like A,B,C, or D, SUAs, etc.). There are no navigational equipment requirements for your aircraft other than to have an operational magnetic compass. Your other equipment dictated in Title 14 Part 91.205(b) are more for general flight than they are for navigation.
That being said, you should not use your phone as your primary means of navigation in any scenario. Instead, rely on your piloting skills as primary and the phone as back up. Have a navigation plan. Make a navigation log. Have well defined landmarks and visual reference points along your route. Have a calibrated compass and compass deviation card as well as an accurate clock with hours, minutes, and seconds. Be able to do compass turns and timed turns. Have an accurate/updated sectional  chart, a plotter, and an E6b (electronic or manual). Etc.
Smart phones, tablets, and apps have come a long way in recent times. The GPS receivers can get an amazing amount of accuracy for what they are. You don’t even need a WiFi or cellular data signal depending on the app you use. I have been able to track my flight as a commercial passenger or my hiking, biking, or driving in foreign countries without an internet signal.
But, don’t rely on them in the air when it matters. I’ve had my phones shut down after the ambient temperature reached 104°F (40°C) on bike rides. I have had my tablets shut down on cool days in the C172 with the windows open just because they spent the entire cross country trip in direct sunlight in my lap. Good old paper and a manual E6b don’t suffer from these drawbacks.

I'm not sure why you say that a pilot must have visual reference to the ground under VFR? VFR over the top is generally legal in the US (see this question).

@quietflyer - That’s a very good question. I guess it is a moot point if you were VFR-on-top because that is an IFR operation. If you were VFR-over-the-top, you required to have all of the equipment stipulated in Part 91.205(d) according to Part 91.507. Technically, I guess it does not say you have to use the equipment. So, would your above comment make your flight in violation of Part 91.507?

@Pondlife - You are right. VFR-over-the-top is legal. Of course, busting an airspace because you did not know where you were is not. If you can maintain positional awareness, you can fly anywhere you want without seeing any visual references. My point in my answer is that doing so would be very unlikely if your gps went out and you had no other navigational aid. Even your compass and clock can only take you from visual reference to visual reference with confidence.

See https://pilotworkshop.com/tips/vfr-over-top/  or https://aviation.stackexchange.com/a/31183/34686 .  In short the answer could be improved by deleting first half of second sentence.

Thanks for reference to FAR 91.507; if I ever knew about it, I forgot.  Gyro instruments are clearly prescribed but "navigation equipment suitable for the route to be flown." is pretty vague-- in some cases I wonder if it could be construed to include instruments suitable for dead reckoning if a very large area of CAVU is known to lie beyond even if presently out of sight?  That could be an ASE question.

Actually FAR 91.507 is in subpart F of part 91 (starts at 91.500) which only applies to "Large and Turbine-Powered Multiengine Airplanes and Fractional Ownership Program Aircraft", so I guess I wasn't busting the regs after all, and my suggested edit still stands.


text:
How do I properly report sighting a drone or hobby UAV to ATC?
How would one go about reporting a drone (hobby UAV) sighted in the airspace of an airport on frequency, specifically to Tower?
For example: I am doing patterns around the airport when to the northeast of my nose I see an object flying through the airport field, looking as though it is a drone entering the airport. What is my responsibility in this situation?

Great question, and I'm not sure there is an entirely established procedure for this yet, as drones are still a relatively new development.
First, your responsibility as a VFR pilot is "See and Avoid".
So if you think its headed towards you, maneuver to avoid it (provided you're not making dangerous, drastic moves!)
Secondly, I'd report it to the tower as:
"Bay View Tower: N227TW:  I see a drone in the airspace, my 2 o'clock, slightly below, less than one mile, headed towards the airport"
At best, the tower may be able to say they're already talking to the drone operator.  Otherwise, tower may simply say, "Roger: keep me updated, deviate from the pattern at your discretion"

Is this a hypothetical, or something you actually encountered?  Would you care to share the details?

For the most part, 'drones' are very similar to the monsters under a child's bed or the 'closet monkey.'  The only difference is a 'drone' is physical to go along with the fear. How many collisions have occurred vs. bird strikes?

How was this handled before drones ... but after RC aircraft as a hobby started (before WW2)?

Make sure to carry this chart in your aircraft so you can identify it correctly.

@TomMcW I tried to make it to through the chart, but it just kept droning on and on.

@AJHenderson Drones can usually be identified by their more rounded body, larger eyes and the lack of a stinger.


text:
Why do we undershoot/overshoot with a compass turn?
In the southern hemisphere you would undershoot when turning towards a southerly heading and overshoot towards a northerly heading, and the opposite in the northern hemisphere. Why is this?

There is a good video that goes over the topic here ~2:45 into the video. It has to do with the way a magnetic compass responds to turns. When turning north the compass lags when compared to the tun of the physical aircraft so you need to overshoot the heading based on what the compass is showing. When turning south the compass leads the turn and you must roll out early to make your desired heading.
This site offers a nice explanation of why this happens in the compas

Northerly turning error is due to the mounting of the compass. Since
  the card is balanced in fluid, when the aircraft turns, the card is
  also banked as a result of centrifugal force. While the card is
  banked, the vertical component of the Earth's magnetic field causes
  the north-seeking ends of the compass to dip to the low side of the
  turn. When making a turn from a northerly heading, the compass briefly
  gives an indication of a turn in the opposite direction. When making a
  turn from the south, it gives an indication of a turn in the correct
  direction but at a faster rate.

Similar explanations show up in this thread. Simply put its not the turn that causes the error but the banking of the aircraft. By rolling the compass housing to one side we allow the compass to tilt differently than it would in level flight. Since the pole is generally beneath the aircraft the roll allows the compass to pitch in a slightly different way causing the error we see.

I didn't see the video actually explain why, except briefly mentioning the “magnetic dip”, but without even saying what it is.

Yeah, ive only known that it is cause by the dip. But how does this dip exactly work/function and why does it happen. Thus how does it lag the compass.

@AgetAviano I found a decent explanation and added it above, if its still unclear I will try and expand more.

@AgetAviano if you want a really detailed answer you may want to ask on Physics.SE

@Dave thanks alot for the additional information. I understand the reason for the lag/lead better now.

Related -- http://aviation.stackexchange.com/a/97267/34686 -- with a caution -- it's not the direction you are turning that matters. It's whether the aircraft's instantaneous heading contains a northerly or southerly component.  This pertains to the second and third sentences of this answer.  Likewise, for deciding whether to roll out "early" ("undershoot) or "late" ("overshoot"), the key factor is whether your intended final heading has a northerly or southerly component, not whether you are turning to the north or to the south.

Similarly, re the quoted content in this answer, the direction you are turning from only matters when describing the behavior of the compass as you are initiating the turn.  When deciding whether to "overshoot" or "undershoot" on the roll-out, all that matters is whether the final target heading contains a northerly or southerly component.  For example, when trying to roll out on a SW heading, you'd plan to "overshoot" regardless of whether you were turning left ("from the north") or right ("from the south").


text:
What is the correct phraseology for "runway 03 R”?
What phraseology is normally used for "runway 03 R" by air-traffic control and pilots?
A couple of possible options I came up with:

runway zero three R
runway three R
runway zero three right
runway three right

Is there any standard or preference of one form or the other to reduce confusion during communication?

Are you asking about a specific country? The US has a different practice here from the rest (?) of the world.

Indeed, in the US that would be "Runway Three-Right" rather than "Runway Zero-Three-Right."

Runway 03 R would be pronounced as

Runway Zero Three Right

As ever, although British, I thoroughly recommend CAP 413 the UK's Radio Telephony manual:
https://publicapps.caa.co.uk/modalapplication.aspx?catid=1&pagetype=65&appid=11&mode=detail&id=6973
It's mostly ICAO compliant and barring small differences, should contain plenty of information for most operations. You'll see all runways are stated using two digits. Unfortunately I can't find an example of parallel runways in there.

One important note

Runway Zero Three Right

Designates runway 03R, as opposed to runway 03L.
However,

Runway Zero Three Righthand

Designates runway 03 and a right hand circuit. Very different things! In real life the chance of confusion is fairly slim, but it's worth noting.

Is there any standard or preference of one form or the other to reduce confusion during communication?

Absolutely. Considerable effort has gone into the standardisation of air traffic communications in order to decrease the risk of misunderstanding. Page 6 onwards of CAP413 above goes into excruciating detail about how to utilise numbers, for example.

Wouldn't the number '3' be pronounced as 'tree'? IIRC there is this convention to prevent the speaker from blowing into the microphone when making the 'th' sound.

It would, I didn't write it phonetically though perhaps I should have. Though to be honest, I find a lot of people don't use the phonetic alphabet for numbers